Abstract Juvenile-onset fibromyalgia (JFM) is a chronic, debilitating pain condition that persists into adulthood for the majority of patients. Our research group has demonstrated that cognitive-behavioral therapy (CBT) is effective in reducing functional disability in adolescents with JFM. However, in order to achieve stronger and clinically meaningful improvement in functional disability and reduce pain, changing sedentary behavior and increasing engagement in moderate-vigorous physical activity is a crucial component of JFM pain management. Incorporation of physical exercise has emerged as a logical next step to enhance CBT, yet regular participation in any physical activity is difficult to initiate and maintain in JFM patients. Our multidisciplinary team of experts in Behavioral Medicine, Rheumatology, Exercise Science and Pain Medicine have developed a novel intervention - the Fibromyalgia Integrative Training program for Teens (FIT Teens), which enhances established CBT techniques with specialized neuromuscular exercise training derived from evidence-based pediatric injury prevention research. Innovative features include 1) progressive neuromuscular training designed to limit delayed-onset muscle soreness; and 2) seamless integration with CBT to enhance psychological coping skills and decrease fear of movement. Our pilot work shows that this intensive group-based 8-week (16-session) intervention is safe, produces excellent patient engagement, has no adverse effects, reduces fear of movement and has a greater impact on pain-related disability than CBT alone. Moreover, these improvements are accompanied objective improvements in strength and movement competence documented via sophisticated 3-D motion capture technology ? indicating greater capacity for safely engaging in physical exercise. This treatment approach is extremely promising in its wide ranging impact on treatment of JFM as well as other chronic musculoskeletal pain conditions in children. In this U01, we propose a rigorous 3-arm multi-site randomized clinical trial (RCT) to test whether the FIT Teens intervention is more effective in reducing disability than CBT alone or graded aerobic exercise alone at the 3-month primary endpoint and whether treatment effects are sustained over 1 year. We will also explore how changes in coping, fear of movement, and objectively measured physical activity, movement competence and physical fitness predict changes in outcomes. The proposed RCT will be the largest (N=420) and most rigorous trial in JFM to date which necessitates a multi-site study with multi-disciplinary collaborators whose complementary expertise ensures success in accomplishing the study aims. Supported by a U34 planning agreement, we have established a robust RCT infrastructure with a central Data Coordinating Center and seven clinical sites, accomplished key administrative and regulatory milestones, completed feasibility assessment and developed standardized protocols for a streamlined transition to a U01 clinical trial. The planned project will provide clear direction for the best clinical care for JFM patients as well as the largest registry of well-characterized JFM patients for potential ancillary projects focused to investigate the pathophysiology of JFM.